This disclosure relates to directional drilling of subterranean wells. Directional or steerable drilling rigs are employed to drill wellbores that deviate by some degree from a vertical path into a subterranean formation. Various types of directional drilling systems have been employed to drill deviated wellbores, including, for example, so-called “point-the-bit” and “push-the-bit” systems. In point-the-bit systems, the bottom hole assembly (BHA) steers the drill bit in a particular direction relative to an axis of the BHA by deflecting a shaft, to deviate from the current borehole path. In push-the-bit systems, a mechanism such as a pad pushes against the formation to cause the drill bit to deviate from the current borehole path.